At some point though the Japanese terminology is just more efficient. What's easier and faster to say? "Sankkyo" or "Dance with me or I'll break your wrist"? Especially since "Dance with me or I'll break your wrist" could be the name of several other techniques...

Not so sure about that Rebecca, I practice a system where all the different attacks have been given numbered forms ie. Shomen uchi = 5th form, Yokomen uchi = 6th form, uke's right hand grabs tori's right wrist = 1st form etc, it seems to me that this is more efficient, no need for an english speaker to learn a new language, and from some of the japanese terms that I've seen they are quite complex.
I admit that if I were to practice in a dojo where japanese was used to describe the attack I may struggle with the words, but once I'd seen the attack I wouldn't struggle with the technique

Having said that we still use the japanese descriptions of the techniques themselves, ikkyo, shihonage etc. after all ikkyo, nikkyo, sankyo, yonkyo is just a numbering system too.

IMO there is no 'need' to keep an art in the language of origin for it to be practiced, in fact it can be an extra layer of complexity that can be and is in some places removed or converted, without loss of any purity of the art.